The present invention relates to wireless networks and more specifically to systems and methods for selecting available channels free of occupying signals from a plurality of radio frequency channels. Embodiments of the present invention provide methods and systems for exploiting licensed and unlicensed bands requiring radar detection and detection of other occupying signals, such as the Dynamic Frequency Selection (DFS) channels in the Unlicensed National Information Infrastructure (U-NII) bands, to enable additional bandwidth for 802.11 a/n/ac and LTE in unlicensed spectrum (LTE-U) networks by using a cloud DFS super master.
Wi-Fi networks are crucial to today's portable modern life. Wi-Fi is the preferred network in the growing Internet-of-Things (IoT). But, the technology behind current Wi-Fi has changed little in the last ten years. The Wi-Fi network and the associated unlicensed spectrum are currently managed in inefficient ways. For example, there is little or no coordination between individual networks and equipment from different manufacturers. Such networks generally employ primitive control algorithms that assume the network consists of “self-managed islands,” a concept originally intended for low density and low traffic environments. The situation is far worse for home networks, which are assembled in completely chaotic ad hoc ways. Further, with more and more connected devices becoming commonplace, the net result is growing congestion and slowed networks with unreliable connections.
Similarly, LTE-U networks operating in the same or similar unlicensed bands as 802.11 a/n/ac Wi-Fi suffer similar congestion and unreliable connection issues and will often create congestion problems for existing Wi-Fi networks sharing the same channels. Additional bandwidth and better and more efficient utilization of spectrum is key to sustaining the usefulness of wireless networks including the Wi-Fi and LTE-U networks in a fast growing connected world.
Devices operating in certain parts of the 5 GHz U-NII-2 band, known as the DFS bands or the DFS channels, require active radar detection. This function is assigned to a device capable of detecting radar known as a DFS master, which is typically an access point or router. The DFS master actively scans the DFS channels and performs a channel availability check (CAC) and periodic in-service monitoring (ISM) after the channel availability check. The channel availability check lasts 60 seconds as required by the Federal Communications Commission (FCC) Part 15 Subpart E and ETSI 301 893 standards. The DFS master signals to the other devices in the network (typically client devices) by transmitting a DFS beacon indicating that the channel is clear of radar. Although the access point can detect radar, wireless clients typically cannot. Because of this, wireless clients must first passively scan DFS channels to detect whether a beacon is present on that particular channel. During a passive scan, the client device switches through channels and listens for a beacon transmitted at regular intervals by the access point on an available channel.
Once a beacon is detected, the client is allowed to transmit on that channel. If the DFS master detects radar in that channel, the DFS master no longer transmits the beacon, and all client devices upon not sensing the beacon within a prescribed time must vacate the channel immediately and remain off that channel for 30 minutes. For clients associated with the DFS master network, additional information in the beacons (i.e. the channel switch announcement) can trigger a rapid and controlled evacuation of the channel. Normally, a DFS master device is an access point with only one radio and is able to provide DFS master services for just a single channel. Significant problems of the current approach include: (1) hidden nodes; (2) hidden radar; (3) false radar detections; (4) long delays in DFS channel switching at radar detection or false radar detection; (5) failure to support geo-fencing of areas of radar use based on external data; (6) underutilization of the DFS spectrum due to the dominance of private access points in the DFS spectrum; (7) interference between proximate LTE-U and Wi-Fi devices; and (8) lack of spectrum-use coordination between devices. The present systems and methods using a cloud DFS super master address these issues with prior art systems.